U.S. patent number 4,734,703 [Application Number 06/774,749] was granted by the patent office on 1988-03-29 for three-wave antenna for vehicle.
This patent grant is currently assigned to Harada Kogyo Kabushiki Kaisha. Invention is credited to Yoshima Egashira, Kazuhiko Nakase.
United States Patent |
4,734,703 |
Nakase , et al. |
March 29, 1988 |
Three-wave antenna for vehicle
Abstract
A three-wave common antenna for AM/FM and ultra high frequency
waves combined in a single unit and mounted on vehicles including
AM/FM antenna element mounted on a vehicle body at its base, a
non-grounded type ultra high frequency antenna element disposed on
top of the AM/FM antenna element such that the beam in a vertical
plane thereof is close to the horizontal direction, a coaxial
feeder cable for ultra high frequency which, along the AM/FM
antenna element, is led into a vehicle body with one end thereof
connected to the ultra high frequency antenna element, a
characteristic compensating circuit connected to the AM/FM antenna
element, and a feeder cable for AM/FM waves connected to the
characteristic compensating circuit.
Inventors: |
Nakase; Kazuhiko (Tokyo,
JP), Egashira; Yoshima (Kanagawa, JP) |
Assignee: |
Harada Kogyo Kabushiki Kaisha
(Tokyo, JP)
|
Family
ID: |
13385643 |
Appl.
No.: |
06/774,749 |
Filed: |
September 11, 1985 |
Foreign Application Priority Data
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|
|
|
|
Apr 1, 1985 [JP] |
|
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60-68853 |
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Current U.S.
Class: |
343/790; 343/715;
343/750; 343/853; 343/905 |
Current CPC
Class: |
H01Q
21/28 (20130101); H01Q 5/48 (20150115); H01Q
5/40 (20150115) |
Current International
Class: |
H01Q
21/00 (20060101); H01Q 21/28 (20060101); H01Q
5/00 (20060101); H01Q 005/00 (); H01Q 021/28 () |
Field of
Search: |
;343/712,711,790-791,713,714,715,725,750,905,830,890,852,853,749 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nussbaum; Marvin L.
Attorney, Agent or Firm: Koda and Androlia
Claims
What is claimed is:
1. A three-wave common antenna for vehicles comprising:
an elongated tubular AM/FM antenna coupled to and extending
outwardly from a vehicle body at a lower end, said AM/FM antenna
not being an optimum antenna length;
a non-grounded ultra high frequency antenna coupled to an upper end
of said AM/FM antenna, a radiation pattern in a vertical plane of
said ultra high frequency antenna being substantially in a
horizontal direction;
a coaxial feeder cable for ultra high frequency, one end of said
coaxial feeder cable being coupled to an input of said non-grounded
ultra high frequency antenna and said coaxial feeder cable being
led inside of the vehicle body along said AM/FM antenna;
a characteristic compensating electric circuit coupled to an input
of said AM/FM antenna for electrically compensating for said AM/FM
antenna not being the optimum antenna length; and
a feeder cable for AM/FM waves, one end of said feeder cable being
coupled to an output of said characteristic compensating electric
circuit.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a three-wave antenna to be mounted
on a vehicle, such as an automobile, and more particularly to an
antenna which is a combination of a ultra high frequency antenna
and an AM/FM antenna.
2. Prior Art
Recently, it has become popular to install various types of
wireless devices such as cellular system radio telephone equipment,
personal wireless equipment, MCA equipment in vehicles such as
automobiles, etc. to be used as movable radio appliances. Ultra
high frequency antennas are necessary for these wireless devices
and such ultra high frequency antennas are installed on the roof,
etc. of the vehicles.
On the other hand, a receiver for AM/FM broadcasting is commonly
provided in automobiles, etc., and almost all cars and other
vehicles are equipped with AM/FM antennas.
Accordingly, the foregoing ultra high frequency antennas, for
example, an ultra high frequency antenna for a radio telephone and
a ultra high frequency antenna for a wireless personal
communication equipment, need to be installed at different
locations from the foregoing AM/FM antennas.
However, installing the ultra high frequency antenna at a different
location from where the AM/FM antenna is installed, for example, on
the roof of a vehicle, diminishes the appearances of the vehicle in
terms of aesthetic design, because installations in the above
mentioned manner result in disorderly mounting of a plural number
of antennas on the vehicle. Furthermore, holes must be provided
separately at a plural number of locations for the installation on
the vehicle body and the work for each antenna installation must be
performed separately. Consequently, installation becomes
complicated and many work steps are required. Besides, the fact
that a plural number of sticklike antennas stick out of the vehicle
body and this is further undesirable for safety reasons while
driving the vehicle.
SUMMARY OF THE INVENTION
The object of the present invention, therefore, is to provide a
three-wave common antenna that is not only capable of receiving
AM/FM waves for general broadcasting, but is also capable of
receiving and transmitting the preferred ultra high frequency waves
according to the required purpose.
A further object of the present invention is to provide a
three-wave antenna which does not hurt the appearance of an
automobile in its design aesthetics.
Still a further object of the present invention is to provide a
three-wave antenna which is desirable also from the viewpoint of
safety while the vehicle is being driven.
In keeping with the principles of the present invention, the
objects are accomplished by a unique structure for a three-wave
common antenna including an AM/FM antenna element, ultra high
frequency (UHF) antenna element, a coaxial feeder cable for UHF
wave, a characteristic compensation circuit, and a feeder cable for
AM/FM waves. The AM/FM antenna is mounted on a vehicle body, and
the UHF antenna element is attached on top of the AM/FM antenna
such that the beam in a vertical plane of the UHF antenna is
approximated to the horizontal direction, and the coaxial feeder
cable, connected to one end of the UHF antenna element, is fed into
the body of the vehicle along the AM/FM antenna element. The
characteristic compensation circuit is connected to the AM/FM
antenna element and the feeder cable for the AM/FM waves is
connected to the characteristic compensation circuit.
As seen from the above, the AM/FM antenna element is provided on a
supporting pole for installing the non-grounded system ultra high
frequency antenna element away from the body of the vehicle. In
this manner, the body of the vehicle avoids effecting the
directivity. Also, the coaxial feeder cable for ultra high
frequency is inserted into the body of the vehicle along the AM/FM
antenna element (in other words, for example, by passing the cable
through the inside of the antenna element). Thus, an antenna that
commonly can be used for three types of waves can be constructed as
a single antenna. Further, characteristics which lower the grade of
the antenna such as insufficient length of the AM/FM antenna
element, which mainly stem from restrictions on the total length of
the antenna for conveniently putting the vehicle in a garage, etc.,
can be avoided by the characteristic compensating electric
circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a structural sketch showing the principle of a three-wave
common antenna according to thepresent invention;
FIG. 2 is a sectional view showing the concrete structure of the
antenna of FIG. 1; and
FIGS. 3 and 4 are perspective views showing the main portions of
the other embodiments of the present invention, respectively.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1, it is a structural sketch showing an
embodiment wherein the present invention is applied to a three-wave
common antenna for automobiles, obtained by combining an AM/FM
antenna with a cellular system radio telephone antenna which is
claiming increasingly expanding demand for its use at the most
important means for communication today and in the future.
In the Figure, numeral 1 denotes a body wall of an automobile. At
the antenna fitting location of this body wall 1, the base of an
AM/FM wave receiving antenna element 3 is fixed. The foregoing
AM/FM antenna element 3 is made of metal pipe, and it serves also
as a supporting pole for an ultra high frequency antenna which will
be mentioned below. At the head of the above mentioned AM/FM
antenna element 3, an ultra high frequency antenna 4, which is used
for a cellular system radio telephone, is disposed. This ultra high
frequency antenna element 4 is an isolated neutral system dipole
antenna element of about 200-300 mm in total length. The feeding
portion 4a of the foregoing ultra high frequency antenna element 4
is disposed at a position separated from the surface of the body
wall 1 by a distance L1 that is longer than one wavelength, in
order to reduce the effect of the body wall 1 on the directivity of
the antenna. Also, this feeding portion 4a is laid out in such a
manner that the beam in the vertical plane approaches the
horizontal direction.
In this case, it is desirable for the total length L2 of the
antenna to be set at about 900 mm or less when parking the car in
the garage is considered. Accordingly, the length of the AM/FM
antenna element 3 that is disposed below the ultra high frequency
antenna element 3 is limited to be about 400-600 mm. This length is
considerably shorter than the length of the antenna for .lambda./4
which is approximately 750-1000 mm in the ordinary FM frequency
band, and it becomes a capacitive one. Consequently, for the FM
wave, the optimum antenna length cannot be obtained, and impedance
mismatching and gain decrease are invited. Also as to the AM wave,
the impedance of the antenna is increased by the portion
proportional to the shortening of the antenna length, and in
relation to the capacity of the feeder line, lowering of
sensitivity is caused. Therefore, in order to compensate for such
degradation in characteristics, a characteristic compensation
electric circuit 7, as will be mentioned later, is provided.
To the aforementioned feeding portion 4a of the ultra high
frequency antenna element 4, one end of a coaxial feeder cable for
ultra high frequency 5 is connected. The other end portion of this
coaxial feeder cable 5 is led inside of the body of the vehicle
through the inside of the AM/FM antenna element 3. A connector 6 is
connected to the other end of the foregoing coaxial feeder cable
5.
An antenna end connection (antenna connecting terminal) 7a of the
characteristic compensating electric circuit 7 is connected to the
feeding portion 3a of the AM/FM antenna element 3. This
characteristic compensating electric circuit 7 is provided to
compensate for the degradation in characteristics, caused by the
insufficient length of the AM/FM antenna element 3. This
characteristic compensating electric circuit 7 includes an
impedance matching transformer A for FM waves and an amplifier B,
in order to compensate for the impedance mismatching as well as
gain reduction as to the FM waves, which are caused because it is
impossible to obtain the optimum length of the antenna. In
addition, an impedance transformer for AM waves C and an amplifier
D are also included in the characteristic compensating electric
circuit 7, in order to compensate for, with respect to the AM
waves, increments of antenna impedance and lowered sensitivity in
relation to feeder line capacity, which are caused by the shortness
(insufficient) of the length of the antenna. With such an
arrangement provided, mutual interference between the AM waves and
FM waves is checked and thereafter, by way of a circuit E for
mixing both types of waves, they are output from the end connection
of the feeder cable 7b.
The coaxial feeder cable 8 for AM/FM waves (hereafter referred to
as feeder cable 8 in order to differentiate it from the coaxial
feeder cable 5) is connected at one end to a feeder end cable
connection 7b. A connector 9 is attached to the other end of the
feeder cable 8. This connector 8 is provided with a built-in
condenser 10 that serves to set the electrostatic capacity on the
antenna side when looked from the plug for the foregoing connector
9 to be 80 PF. Numeral 11 is a power supply line for supplying DC
power for operation to the electronic circuit of the characteristic
compensating electric circuit 7.
FIG. 2 is a sectional view showing the concrete structure of the
three-wave common antenna (an antenna commonly used for three types
of different waves) in FIG. 1. As shown in FIG. 2, the outer
circumferential surface of the ultra high frequency antenna element
4 is covered with a protective pipe 12 made of reinforced glass
resin (FRP). The root 12a of this protective pipe 12 is connected
to the head portion of the AM/FM antenna element 3, by press
fitting, adhesion, or other means. At the head 12b of the foregoing
protective pipe 12, a cap 13 for preventing the intrusion of
rainwater, etc. is mounted. The upper end portion of the coaxial
feeder cable for ultra high frequency 5 is fixed to the upper end
open area of the metal pipe constructing the AM/FM antenna element
3, by being supporting by a supporting member 14. The central
conductor 5a and the outer conductor 5b of the foregoing coaxial
ultra high frequency feeder cable 5 are connected to the feeding
portion 4a of the ultra high frequency antenna element 4.
The AM/FM antenna element 3 and the coaxial feeder cable 5 are led
inside the vehicle body through a fitting hole 15 in the body wall
1. Onto the outer circumferential surface of the portion of the
body wall through which the antenna element 3 passes the body wall
1, as well as the outer circumferential surface of the portion
along which the antenna element 3 is led into the vehicle body, a
bottomed, cylindrical form insulating cylinder 16 is fit from
below. Furthermore, a cylinder 17 made of metal is fitted onto the
outer circumferential surface of the insulating cylinder 16.
The coaxial feeder cable 5 inserted into the antenna element 3 is
led downward by passing through the center of the bottom wall 16a
that closes the lower end of the insulating cylinder 16. At a part
of the outer circumferential surface of the bottom wall 16a, a
protruding portion 16b is formed. This protruding portion 16b
sticks out to the outside of the cylinder 17, through a hole formed
at the center portion of the circumferential wall of the cylinder
17. At the center of the protruding portion 16b mentioned above, a
connecting wire 18 is provided. This wire 18 will make a connection
between the feeding portion 3a of the antenna element 3 and the
antenna end connection 7a of the characteristic compensating
electric circuit 7.
The outer circumferential wall of the upper end portion of the
cylinder 17 is fit and fixed to the body wall 1, by means of a
fitting assembly 20 that corresponds to a fitting means 2 shown in
FIG. 1. The fitting assembly 20 is formed of a lower fitting
element 20A and an upper fitting element 20B. The fitting element
20A also serves as ground fittings.
The lower fitting element 20A includes a conductive ring member 21
and contact members 22. The conductive ring member 21 is fixed into
the outer circumferential surface of the cylinder 17. The contact
members 22 are conductive, and these conductive contact (pad)
members 22 are protrude at a plural number of locations on the
foregoing conductive ring member 21, such that they can come into
contact with the underside of the body wall 1.
The upper fitting element 20B includes a pad 23, an adjustable
fitting seat 24, and a lock nut 25. The pad 23 is made of soft
material, such as rubber, and is fit onto the protruding portion of
the cylinder 17, that is sticking out to the outside of the body
wall, in a form which comes into contact with the surface of the
body wall 1. The adjustable fitting seat 24 is made of hard
synthetic resin, etc. in a hemispherical shape. The same as the pad
23, this adjustable fitting seat 24 is fit over the protruding
portion of the cylinder 17, and is disposed in a form to be mounted
on the pad 23. The lock nut 25 is made of hard material, such as
metal, and as the pad 23, the seat 24 is fit onto the protruding
portion of the cylinder 17, by being screwed to an external thread
formed over the outer circumferential surface of the foregoing
protruding portion of the cylinder 17. This lock nut 25 is disposed
in such a manner that the bottom surface of the lock nut 25 is
pushed into contact with the adjustable fitting seat 24.
By means of the foregoing structure, this fitting assembly 20
safely and reliably fit the whole body of the antenna to the body
wall 1, through clamping the lock nut 25 while setting the whole
body of the antenna vertically by adjusting the adjustable fitting
seat 24 according to the inclination of the fitting surface of the
body wall 1.
The coaxial feeder cable 5 led downward by passing through the
center of the bottom wall 16a of the insulating cylinder 16 is
further led into the vehicle body through the center area of a
cable fixing assembly 30 which is fit to the opening portion of the
lower end of the cylinder 17. The cable fixing assembly 30 is
formed of a fixing seat 31 and a holding member 32. The fixing seat
31 is made of synthetic resin, etc. in a disc form, and is fixed at
the opening area of the lower end of the cylinder 17, by roll
caulking or other methods. The holding member 32 is combined with
the center portion of the upper end surface of the fixing seat 31
to hold the coaxial cable 5, by tightly pressing it from outside.
In this way, the cable fixing assembly 30 fixes the coaxial feeder
cable 5 so that it does not easily slide in the longitudinal
direction.
To the portion of the outside surface of the cylinder 17 where the
protruding portion 16b is sticking out, a case 40 that houses the
characteristic compensating electric circuit 7 is provided. This
case 40 includes a first portion 41 that is disposed on the fitting
side and a second portion 42 that is joined to the first portion 41
to form a single unit together with the first portion. The first
portion 41 is fixed to the cylinder 17 by means of a plural number
of set screws 43. The second portion 42 is joined at its opening
area to the opening area of the first portion 41 by means of
waterproof packing 44. Furthermore, the second portion 42 is fixed
to the first portion 41 by means of a plural number of set screws
45.
The antenna end connection 7a of the characteristic compensating
electric circuit 7 that is housed in the case 40 is connected to
the one end of the previously mentioned connecting conductor 18. On
the other hand, the feeder cable end connection 7b of the
characteristic compensating electric circuit 17 is connected to a
cable conductor 8a that is the inner conductor of the feeder cable
8 led into the case 40 by passing through the waterproof packing
44. A braided wire 8b, that is the other conductor of the feeder
cable 8, is connected to the inside bottom portion of the first
portion 41 to be grounded. The DC power line 11 of the
characteristic compensating electric circuit 7 passes through the
waterproof packing 44 together with the feeder cable 8.
In the embodiment constructioned as described above, the AM/FM
antenna element 3 is disposed at the location for a supporting pole
that is to serve to install the isolated neutral system ultra high
frequency antenna element 4 by separating it from the body wall 1
in order to avoid the effect of the body on the directivity. Also,
it is designed that the coaxial feeder cable for ultra high
frequency is inserted in the vehicle body through the inside of the
AM/FM antenna element 3. Therefore, an antenna which can be used
for three different types of waves is formed by a single
antenna.
Degradation in characteristics due to insufficiency in length of
the AM/FM antenna element 3, which is caused by restriction on the
total length of the antenna taking into such conditions as parking
the vehicle in a garage, can be sufficiently compensated for by the
characteristic compensating electric circuit 7.
The present invention is not limited to the foregoing embodiment.
For example, in the embodiment mentioned above, a metal pipe 3 is
used as the AM/FM antenna element 3 and this metal pipe is used as
a supporting pole for fitting the non-grounded system ultra high
frequency antenna element 4 at a location away from the body wall
1. However, as shown in FIGS. 3 and 4, instead of the metal pipe,
reinforced glass resin (FRP fiber reinforced plastics) pipe 50 may
be used. At the same time, as shown in FIG. 3, a metal wire 51 may
be provided along the inner circumferential surface of the FRP pipe
50 to be used as the AM/FM antenna element. Further, as shown in
FIG. 4, a conductor 52 may be coiled into a helical shape around
the outer circumferential surface of the coaxial feeder cable 5 to
be used as the AM/FM antenna element. In the modified embodiment in
FIG. 4, the length of the AM/FM antenna element can be virtually
shortened.
The metal wire 51 and the helical conductor 52 shown in FIGS. 3 and
4 are not necessarily disposed inside of the FRP pipe 50. They may
be provided along the outer circumferential surface of the FRP pipe
50, depending on necessity. Furthermore, in the foregoing
embodiment, as the AM/FM antenna element 3, a single metal pipe is
used. However, a plural number of metal pipes with different
diameters may be slidably connected to form a multistage system
antenna element which may be retracted into the body of the
vehicle. In this case however, the coaxial feeder cable 5 must be
disposed so that it does not interfer with the sliding movement of
the antenna as mentioned above.
In addition, in the above described embodiment, the characteristic
compensating electric circuit 7 is housed in the case 40. However,
if the electric circuit 7 is small in size it may be stored in the
space 17a formed below the cylinder 17. Besides, in the above
described embodiment, a non-grounded system dipole antenna 4 is
used as the ultra high frequency antenna element for cellular
system radio telephones. However, the ultra high frequency antenna
element is not limited to that use only but can also be used for
personal wireless antennas, MCA equipment antennas and may be
employed in many other uses. Also, not only a dipole antenna, but
also a colinear antenna may be used instead in order to increase
gain.
Moreover, it should be obvious that though the present invention is
described in terms of three-wave common antennas for automobiles in
the above described embodiments, it is also applicable to many
different kinds of vehicles in addition to automobiles. It should
further be understood that various changes and modifications could
be made without departing from the spirit and scope of the present
invention.
It should be apparent from the above description that the present
invention is advantageous in various ways as summarized below.
The AM/FM antenna element is provided at a location where the
isolated neutral system ultra frequency antenna element is
separated from the vehicle body in order to eliminate the effect of
directivity from the vehicle body. Also, the coaxial feeder cable
for ultra high frequency is fed inside of the vehicle body along
the AM/FM antenna element (for example, by passing through the
inside of the foregoing antenna element). Therefore an antenna
which is commonly used for three different types of waves is
contained in a single antenna.
Furthermore, degradation in characteristics due to insufficient
length of the AM/FM antenna element, that in turn restricts the
entire length of the antenna, can be compensated for by the
characteristic compensating electric circuit. Therefore, it is much
easier to park the vehicle in a garage and/or for the vehicle to
enter garages with low overhangs, etc. As a result, the three-wave
common antenna is of course capable of receiving AM/FM waves for
ordinary broadcasting and is also cable of transmitting and
receiving specified ultra high frequency (ultra short wave)
according to the required need. In addition, the antenna does not
hurt the appearance of the automobile in terms of aesthetic design
and is also desirable in terms of safety when the automobile is
driven.
* * * * *